1. Field of the Invention
The present invention relates to a carbon nanotube (“CNT”) film having a transformed substrate structure and a manufacturing method thereof. More particularly, to a CNT film with a transformed substrate structure and a manufacturing method thereof in which the substrate structure is transformed by a structure formed on the substrate, and a CNT solution is applied thereto to form a patterned CNT film to thereby increase the transparency of the CNT film and the electrical conductivity of an electrode manufactured using the CNT film.
2. Description of the Related Art
A display requires a transparent electrode which is electrically conductive. Currently, the transparent electrode used is made of an Indium Tin Oxide (“ITO”). Several problems occur with the use of ITO electrode, in that as the consumption of Indium is increased, the cost is increased, and that resistance thereof increases due to cracks occurring especially when bending an ITO electrode, which case is hardly applied to a flexible device.
Thus, it is desired to develop a transparent electrode applicable to a flexible device, and recently a CNT transparent electrode has been used. A CNT transparent electrode has excellent electrical conductivity and strength, and flexibility, so that the flexible transparent electrode using the CNT can be widely applicable as an electrode material to an energy device such as solar cells or secondary cells as well as a display device such as an existing liquid crystal display (“LCD”), an organic light emitting diode (“OLED”), and a paper like display.
The most important characteristics of the CNT transparent electrode may be electrical conductivity, transparency, and flexibility. Generally, the CNT transparent electrode is manufactured in such a manner that CNT powders are dispersed in a solution including a dispersing agent to prepare a CNT solution, and a plastic substrate is applied with the CNT solution. The important one to improve the conductivity of the CNT transparent electrode is that carriers move CNT itself and freely move between the CNTs.
If the amount of the CNTs in a transparent electrode composed of a CNT network structure is greatly sufficient to bring into contact between CNTs, i.e., above a percolation threshold, resistance of CNT itself hardly affects a CNT network structure film, whereas contact resistance between CNTs mainly has influence upon resistance of the CNT network structure film. Thus, the formation of the CNT network structure and the reduction in contact resistance between CNTs are very important to improve the conductivity of the CNT transparent electrode.
However, the CNT transparent electrode has a limit to obtain high conductivity at high permeability because the CNT solution is applied onto the whole electrode substrate. Thus, the present invention is intended to improve the permeability as compared to the case having the same conductivity through a structure control that is, forming a pattern on the transparent substrate to have a portion on which the CNT solution exists and a transparent portion on which the CNT solution does not exist. Herein, if the CNTs are to serve as an electrode, the structure of the transparent portion should be controlled such that all the CNTs on the substrate are connected together.